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warped knifes after heat treat

C

corkyzach

Joined
Aug 24, 2016
Messages
15
hey all i'm pretty new to knife making and the past few blades I've made the steel ends up warping after i dunked it in the quench oil i don't know if its my technique or what... the steel i'm using is 1075 hcs and the quench oil i have is like a parks 50 equivalent i made a propane forge with fire bricks and a burner i get the steel up past non magnetic then relatively slowly dunk the blade all the way in i get a good solid treatment just my blades warp and their (+-) .001-.003 thousandths straight before i start. sorry for the paragraph i just wanted to be through thanks for any advice
 
Move the blade forward and back in a slicing motion in the quench, not side to side. Make sure your blade is evenly ground. You can straighten with gloved hands once the steel stops hissing and bubbling but BEFORE it gets down below 400 or so.
 
i have noticed if my grinds are not symmetrical on each side, i usually get a warp. just like a japanese blade acquires sori, or a bending upward of the spine during the quench because of the differing thicknesses. in the past when i have quenched blades under .022" i would get bacon edge. the edge warps like the side of a piece of bacon, wavy. yesterday i decided to sacrifice a blade that was already finished to practice hamons. the blade was totally finished to 1500 grit with a previous failed hamon. the edge was @ .010" for the quench. i was shocked to notice the edge warp was so minimal a few passes with 220 grit made it disappear. the warp was less than .002 from the centerline. i can only contribute this to being careful that the edge is centered in relation to the spine, and the tops of the bevels are the same distance from the spine because i check them with calipers. i also agree that side to side movement in the quench is also not good to do.
 
thank you so much for the advise! the blade itself is actually pretty good where their warping is mostly in the shape of a "C" or "U" motion and I've tried to fix that with a bench vise and 3 bolts to straighten it out but its not turning out so good but i will try the slicing motion next time and hopefully that solves my problem thanks again
 
Slight warp is just something that is going to happen from time to time and learning to correct it is part of knife making. If I miss my chance to straighten out of the quench then I fix it during tempering. On the first tempering cycle, I will clamp the blade to a 12' piece of 1/2" flat bar stock. If there is still warp present after the first cycle, then I use shims and clamps on the bar (same idea as the 3 bolts in the vice) to reverse the warp and it goes in for the second tempering cycle. If it still needs work, I drop the temperature by about 30 degrees and increase the counter bend bit by bit with a 45 minute cycle in the oven each time.
 
There may always be stresses in the steel from the mill. To remove them a sub-critical anneal , 1200 F for two hours will remove them .The straighten if necessary. then HT. during quench always agitate by moving the blade edge to spine never side to side .
 
Tell me about it... I've been repeatedly tempering the latest knife I'm working on clamped to a file with counterbend to get the warp out of it. It's very close to straight except for a teeny bit of bacon edge from going too thin at the edge pre-HT. I've been purposely grinding my most recent kitchen knives with asymmetrical grind, and it always warps the in the direction as expected. Still haven't had to give up the ghost on one yet, cross my fingers... :)
 
I use two aluminum angle irons in a vice. With a little bit of play in them to conform to distal tapers.
 
There are two basic types of distortion in knife making. Twisting and bowing, get something flat to check straightness on. Not difficult but takes practice to straighten things.

Knife making is a life time of flattening and straightening.

Hoss
 
Thanks I like the angle iron idea I'm happy I don't have any twisting or bacon edge it just bent about 3/16ths around the middle of the blade right before the finger choil and maybe 5/64ths just before the tip but thanks again will use this knowledge for the next one
 
I've recently run into the problem. I think I put a shaped out blade into a forge that was too hot? Or, I got it too hot too fast? Is that possible? I got the bacon warp (I've been calling it Ruffles Potato Chip edge) and I got a bow on top of it.

I ground-out the bacon, but was left with a warp that will not go away. I tried using a torch and the bow came back. I tried tempering (not clamped to anything) and the bow refuses to relent. I'm going to try clamping it onto a thicker stock while in a temper cycle.

Question: What's the best temperature for that? I normally do 400 for two hours, but in this case, should I change my recipe? Also, for how long?

Thanks!
 
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